MUSCLE AND NERVE 



49 



reactions commonly alternate with perfectly normal ones. The reason 

 for this is not known. Heat neutralizes the influence of veratrin. 



Annotation. In order to economize, the other gastrocnemius muscle of the 

 frog used for the preceding experiment may be immersed for a few moments in a 

 1 per cent, solution of veratrin. If it is then adjusted in the recording apparatus, it 

 will give characteristic veratrin contractions. 



FIG. 28. THE EFFECT OF VERATBIN ON MUSCULAR CONTRACTION. 



3. The Effect of Excessive Stimulation on Contraction. Fatigue. 



Attach a fresh gastrocnemius muscle to the recording apparatus. Put 

 a 10-gram weight in the scale pan. Arrange the electric apparatus for 

 stimulation with single induction shocks of moderate strength. Make 

 the current. Allow the drum to revolve at a rapid rate and break the 

 current after the writing point has passed the line where the paper has 

 been glued together. Turn the drum by hand to the end of the paper 

 without removing the writing lever. Now stimulate the muscle at brief 

 intervals with twenty-five make and break shocks. After the twenty- 

 sixth make contraction hold the bridge of the key down. Allow the 



FIG. 29. FATIGUE OF MUSCLE. 



A gastrocnemius muscle of the frog stimulated successively 150 times. 

 100th, and 150th contractions are recorded. 



The 1st, 50th, 



drum to revolve and record the twenty-sixth break contraction directly 

 after the first. Again stimulate the muscle twenty-five times near the 

 line where the paper has been pasted together, and record the fifty- 

 first break contraction as described. Repeat this procedure, recording 

 the contractions at these intervals until the muscle ceases to lift the 

 lever. Compare the different curves with one another, noting their 

 relative heights and lengths. Wherein does fatigue betray itself? Wait 

 five minutes and stimulate the muscle again. Does it regain its power 

 of contraction? Compare its behavior with that of a normal muscle 

 after excessive exercise. 



